1. Field of the Invention
The present invention relates to a base member having a cylindrical internal surface and a thermally sprayed coating formed on a section of the cylindrical internal surface that has been formed into a rough surface. The present invention further relates to a cylindrical internal surface processing method and a cylindrical internal surface processing apparatus.
2. Background Information
Typically, aluminum engine blocks of internal combustion engines have cylinder liners provided in their cylinder bores. From the viewpoint of improving the output, fuel economy, and exhaust performance of internal combustion engines having aluminum cylinder blocks and from the viewpoint of reducing the size and weight of such engines, there is a very high demand for an engine design that eliminates the cylinder liners that are used in the cylinder bores of aluminum engine blocks. One alternative to cylinder liners is to use thermal spraying technology to form a thermally sprayed coating on the internal surfaces of the cylinder bores.
When thermal spraying technology is applied to a cylinder bore, a coating is formed on the internal surface of the cylinder bore using a thermal spray gun configured to spray molten coating material. The coating is deposited by moving the thermal spray gun in the axial direction inside the cylinder bore while rotating the thermal spray gun. After the thermally sprayed coating is formed, the surface of the coating is finished by grinding using a honing process or other machining process.
Before such a thermally sprayed coating is deposited, the internal surface of the base material of the cylinder bore is roughened using, for example, the surface treatment proposed in Japanese Laid-Open Patent Publication No. 2003-213399 (see FIGS. 2 to 7). The surface roughening serves to improve the adhesion of the thermally sprayed coating.